Transcriptome profiling of the gonad during sex differentiation in hermaphroditic brown-marbled grouper (Epinephelus fuscoguttatus)

Sex differentiation is an intricate process regulated by a complicatedly organized network especially in hermaphroditic fish. The brown-marbled grouper (Epinephelus fuscoguttatus) is a protogynous hermaphroditic fish, however, the regulatory mechanism of its sex differentiation is still unclear. In present study, transcriptome sequencing of the gonads at 117 dph and 259 dph was performed to explore the molecular mechanism underlying sex differentiation. A total of 37,434,906,973 clean reads were generated from six cDNA libraries. QPCR results of 12 genes related to sex differentiation indicated the reliability of transcriptome data. RNA-seq data showed that the genes in retinoic acid signal pathway participate in the early stage of sex differentiation. When the oocyte was observed in histology, the germ cell had finished the preparation of first meiosis with high expression of many meiosis-related genes, including sycp1, sycp3, mlh3, crem, spo11, msh5, and rec8. The germ cells in 259 dph gonad were classified into six stages by their histological morphology. Besides, male-related genes, gsdf, sox9, dmrt1, and dmrt3, might play roles in sex differentiation. Our study, for the first time, investigated the transcriptome from brown-marbled grouper, and identified functional genes, GO terms, and KEGG pathways involved in sex differentiation. These data will contribute to future studies on the molecular mechanism of sex differentiation in teleost.